Postgraduate V.A. Grigoryev²
Associate Professor, PhD L.V. Bulykina¹
Postgraduate A.Yu. Grigoryeva^2
1Russian State University of Physical Culture, Sport, Youth and Tourism (SCOLIPC), Mos-cow
²Faberge College, Moscow

Keywords: blocker movement, kinematic characteristics .

    Introduction. Volleyball is one of the most dynamically developing sports. Optimisation of game actions is the most important volleyball-related challenge sport science faces.   

The review of scientific and instructional manuals and research made by the authors has proven a lack of any recommendations for a particular method the blocker is to employ to move at various distances along the net, depending on the attacking actions of the opponent.   

Game process in volleyball consists in attacks and defences alternating for each team [4,5,6]. Attacks, implemented as versions of a spike, are the main method of offence; they are preceded by a preparatory action of a setter, i.e. second pass for attack [2,5].

 Alternating lengths and directions of passes assure all the game portion of the net be used for attack, and a player of the attacking team may attack in various zones of a play court [2].

Table 1 shows classification of passes:

Table 1. Classification of Second Passes to Arrange Attacks of the Partner

Defending side uses blocking (single or group), the main method of defence, to repulse attacks of the opponent. The central blocker, in his/her turn, is to move to the zone of anticipated attack for group blocking; while moving between the zones, the player predicts the place of attack by the trajectory of a ball after the second pass of the setter, and simultaneously begins moving [2,7].

Three methods of the blocker movement along the net are widely known; they are cross-step, side-step, turn-step-turn. The latter is performed as follows: during a cross-step, a hip joint turns in the direction of movement, while shoulders remain as parallel as possible to the net; in a final step, a foot should be placed as much as possible at a right angle to the centerline; conventionally, we call it a combined method  [4,7].

Objective of the research was to find the best methods of movement for volleyball players of different qualifications to set group block.

Methods and structure of research. Our analysis of game video records revealed the following methods of movement, depending on players’ qualifications (Table 2):

Table 2. Methods of Movement Blockers Use for Various Distances (%)

Note: S - side-step; C - combined step; X - cross-step.    

Table 1 proves blockers prefer side-step (62.8 – 74.0%) for moving at rather short distance (0.5-1.5 m), while combined step (up to 100%) is employed at longer distances (1.5 – above 3 m). Cross-step is hardly used in modern volleyball.   

To determine the fastest method of moving at various distances, we conducted a laboratory experiment using Qualisys, an electrooptical and dynamometric hardware and software complex that works on Qualisys Track Manager (QTM) B Visul 3 D (CMotion) software. QTM program collected primary data from six high-speed video cameras Ogus 3^rd series.       

The research involved 20 elite volleyball players. They were to use different methods for three attempted movements at particular distances defined by markers attached to the floor. Infrared light of the camera highlighted passive markers fixed on the persons tested (centre of mass) and on the floor and recorded reflected signals.      

Time was determined by the moment of meeting between the markers at the body of the person tested (centre of mass) and that on the floor. Table 3 shows the results of research.

Table 3. Kinematic Characteristics of Movement Methods

Results and Discussion. For distances shorter than 1.5 m side-step is the fastest method of movement (0.45 and 0.64 s, respectively), while for longer distances combined method is better (0.66, 0.67 and 1.17 seconds, respectively). 

To optimize game actions, it is wise to correlate the time of the ball flight at various versions of passes made by attacking side, and the time the central blocker needs for employing various methods of movement at a preset distance.  

Table 4 shows relations between the times the blockers need to move at various distances and the times of the second passes required for the spike.

Table 4. Times of Ball Flight during the Second Pass of the Attacking Side vs. Movement Times of the Central Blocker (seconds)

Findings. The research conducted resulted in the following findings:

• Lesson observation revealed the most frequently practiced methods of blocker’s movement
• The experiment defined the time the central player needs for various methods of movement  
• The experiment substantiated that side-stepping of the central blocker can only be effective when the offense makes half-length medium second pass
• In case the attacking side employs all types of passes except of half-length medium, short low (which we omitted as this pass is a part of a combination), combined step is the best method for the central blocker to move.

References

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